American Wildlands v. Norton

The court holds that the U.S. Fish and Wildlife's (FWS') decision that the westlope cutthroat trout (WCT) did not warrant listing as an endangered or threatened species was arbitrary and capricious. The FWS concluded that listing the WCT under the Endangered Species Act was unwarranted because viable, self-sustaining WCT stocks remain widely distributed throughout the species' historic range and because small headwater populations of WCT are relatively secure. The court first holds that the FWS' listing determination for WCT does not reflect a reasoned assessment of the statutory listing factors on the basis of the best available science. The inclusion of hybrid WCT stocks in the viable population of WCT considered for listing was arbitrary and capricious. Although the FWS indentified hybridization as an ongoing threat to the WCT, the record is devoid of any evidence that the agency evaluated that threat in determining whether the WCT population was viable. Moreover, once it identified hybridization as a threat, the FWS nevertheless included hybrid fish in the population considered for listing. If hybridization is a threat, it seems logical that hybrid stock should not be included in the population of WCT reviewed for protected status. The court, therefore, remands the WCT listing determination for reasoned decisionmaking. Also on remand, the FWS must reconsider the threats to isolated headwater populations of WCT in light of the new WCT population it determines to be appropriate for listing evaluation.